Currently, some smartwatches in the industry have a function: with slight rotation of an arm, a screen of a watch is lit up automatically, and time is display on the screen. A principle of the function is as follows: a gravity sensor detects a status of the watch in real time, and when the watch is inclined downward relative to a horizontal plane, and an angle of inclination is greater than an angle threshold (for example, 30°), the screen is lit up automatically.
However, there is one problem: when the screen is lit up, time before the screen is locked is first displayed, and then current time is displayed, resulting in an obvious delay (or an obvious rapid change). The reason is: what is buffered in a framebuffer (FB) of a smartwatch is an original clock display user interface (UI), and only when the screen is lit up, a latest time value is acquired and a latest clock display UI is displayed, causing a rapid time change when the screen is lit up.
In the prior art, a similar problem (that is, a problem of a rapid time change when a screen is lit up) also exists in Android phones. A basic screen locking procedure of an Android system is as follows: When a user presses a power button to lock a screen, the system generates a lock screen UI and buffers the lock screen UI in an FB (note: a clock displays current time), and then the screen goes black, and the system sleeps; when the user presses the power button again, the system is awaken, the screen is lit up, and at this time, the lock screen UI buffered in the FB is displayed (note: the clock still displays the time that is before the screen is locked), and then the system acquires a latest time value, refreshes the lock screen interface, and displays a latest clock value. In the foregoing process, the problem of the rapid time change on a clock (that is, displaying old time before displaying new time) is caused.
There is a solution to the foregoing problem among the Android phones now. For example, in a standby situation, a system periodically acquires a time value and refreshes a lock screen UI. In this way, when a power button is pressed and a screen is lit up, generally, a latest time value is displayed, and the problem of the rapid time change does not occur. However, in the foregoing optimization solution for phones, periodically acquiring time and updating the lock screen UI in a background causes meaningless power consumption, thereby shortening a standby time. Therefore, it is not applicable to electronic devices having an extremely strict requirement on power consumption such as smartwatches.